
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>图片放大镜测试1   但是放大镜的位置无法悬浮</title>
                    
            
</head>
<style type="text/css">
        *{
            margin: 0px;
            padding: 0px;
        }
        body{
            width: 960px;
            margin:40px auto;
        }
        #small{
            width: 300px;
            height: 200px;
            border:1px solid #eee;
            border-radius: 4px;
            position: relative;
        }

        #small img{
            width: 100%;
            height: 100%;
        }

        div    {
            float: left;
            margin-right: 10px;
        }

        #big{
            width: 300px;
            height: 200px;
            overflow: hidden;
            position: relative;
            border:1px solid #eee;
            border-radius: 4px;
            display: none;
        }

        #look_girl{
            position: absolute;
            left: 0px;
            top:0px;
        }

        #move{
            width: 100px;
            height: 100px;
            background:#000;
            opacity: .5;
            position: absolute;
            display: none;
            left: 0px;
            top: 0px;
        }

        .xx{
            width: 300px;
            height: 200px;
            border:1px solid #eee;
            border-radius: 4px;
            position: relative;
        }
         .xx img{
            width: 100%;
            height: 100%;
        }
    </style>
<body>
<h3>https://juejin.im/entry/5a5cbb006fb9a01c975a3b8e</h3>

    <div id="small">
        <img src="img/一切都是穷的错.png">
        <p id="move"></p>
    </div>
    <div class="xx">
        <img src="img/一切都是穷的错.png">
        <p id="move"></p>
    </div>
    <div class="xx">
        <img src="img/一切都是穷的错.png">
        <p id="move"></p>
    </div>
    <div id="big">
        <img src="img/一切都是穷的错.PNG" id="look_girl">
    </div>



    <script type="text/javascript">
    var move = document.getElementById('move');    
    var small = document.getElementById('small');
    var big = document.getElementById('big');
    var look_girl = document.getElementById('look_girl');
    small.onmousemove = function(event){
        event = event || window.event;
        this.style.cursor = 'move';
        // 计算move移动块的left值
        var move_left = event.clientX - this.offsetLeft - move.offsetWidth/2;
        // 计算move移动块的top值
        var move_top = event.clientY - this.offsetTop - move.offsetHeight/2;
        // 超出左边界赋值为0
        move_left = move_left < 0 ? 0 : move_left;
        // 超出右边界赋值为盒子宽度-移动块的宽度
        move_left = move_left > this.offsetWidth - move.offsetWidth ? this.offsetWidth - move.offsetWidth : move_left;
        // 超出上边界赋值为0
        move_top = move_top < 0 ? 0 : move_top;
        // 超出下边界赋值为盒子高度-移动块高度
        move_top = move_top > this.offsetHeight - move.offsetHeight ? this.offsetHeight - move.offsetHeight : move_top;
        // 修改移动块left、top值
        move.style.left = move_left + 'px';
        move.style.top = move_top + 'px';
        /*
            计算图片需要移动的坐标

            距离左边left    图片宽度      盒子宽度          距离左边left    图片宽度           盒子宽度
            big_x/(look_girl.offsetWidth-big.offsetWidth) = move_left/(small.offsetWidth-move.offsetWidth);

            big_y/(look_girl.offsetHeight-big.offsetHeight) = move_top/(small.offsetHeight-move.offsetHeight);

        */

        var big_x = move_left/(small.offsetWidth-move.offsetWidth) * (look_girl.offsetWidth-big.offsetWidth);
        var big_y = move_top/(small.offsetHeight-move.offsetHeight) * (look_girl.offsetHeight-big.offsetHeight);
        // 修改图片定位
        look_girl.style.left = -big_x + 'px';
        look_girl.style.top = -big_y + 'px';
    }

    small.onmouseover = function(){
        move.style.display = 'block';
        big.style.display = 'block';
    }

    small.onmouseout = function(){
        move.style.display = 'none';
        big.style.display = 'none';
    }
</script>

</body>
</html>
